This application claims priority to Great Britain Patent Application No. 9920869B, filed on Sep. 4, 1999.
This invention relates to a latch for doors and the like, and particularly to a door latch of a vehicle.
Known passive entry type car door lock systems work by the driver having about his person a radio frequency card which, as he approaches his own vehicle, is recognized by the vehicle and the vehicle then unlocks itself. On certain passive entry systems the recognition process only starts when an outside door handle is initially moved by the driver. Under such circumstances the electrical power actuator which unlocks the door does so in a fraction of a second and before the door handle has been fully lifted, thus allowing the opening of the door.
However, if the door handle is lifted quickly it can beat the unlocking actuator leaving the door locked with the handle in the up position. The driver must release the handle and then lift it again to open the door, and this can be frustrating to some drivers.
One known solution to this problem is to provide an actuator which both unlocks and also unlatches a door latch. However, significantly more power is required to unlatch than to unlock thus requiring a bigger actuator.
According to the invention there is provided a latch comprising a housing, a locking member of the housing movable between locked and unlocked conditions, a latch release member of the housing movable between closed and open conditions and a latching member of the housing movable between latched and unlatched conditions, movement of the latch release member to the open condition causing movement of the latching member to the unlatched condition when the locking member is in the unlocked condition, and movement of the latching member to the unlatched condition being prevented when the locking member is in the locked condition, wherein an energy storage device is provided between the latch release member and said latching member, and a blocking member of the housing is movable from a disengaged condition to an engaged condition in which movement of said latching member to the unlatched condition is prevented when the locking member is in the locked condition, movement of the latch release member to the open condition causing said energy storage means to bias said latching member to the watched condition when said blocking member is in the engaged condition, movement of said blocking device to the disengaged condition permitting movement of said latching member to the unlatched condition under the action of said bias.
The present invention overcomes the prior art problems by storing energy in e.g. an unlatching spring. If the driver opens the door handle quickly, the spring energy is used to unlatch after the power actuators have unlocked the door. If the driver opens the door handle slowly then the spring is not required to store or release energy.
Preferably the locking member, latching member, latch release member and blocking member are pivotally mounted on said housing. In the preferred embodiment, the blocking member is movable in the opposite sense to the locking member. The latching member and latch release member may be pivoted about the same axis. The energy storage device may be a tension spring.
The locking member may include a force transmission element insertable between the latching member and the latch releasing member in order to transmit motion therebetween in the unlocked condition.